pγ interactions in Galactic jets as a plausible origin of the positron excess

Gupta, Nayantara; Torres, D. F.

doi:10.1093/mnras/stu770

Cited by 22 publications

(21 citation statements)

References 39 publications

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“…We conclude that two nearby pulsars are disfavored as the dominant sources of the positron excess at ∼50-500 GeV in the two-zone diffusion models with the usual Kolmogorov-type diffusion coefficient. In this case, the positron excess must be largely contributed by other sources, such as other pulsars, other types of nearby cosmic accelerators such as supernova remnants (Fujita et al 2009) and microquasars (Gupta & Torres 2014), or even the annihilation or decay of dark matter particles (e.g., Bergström et al 2009;Yin et al 2009;Cholis & Hooper 2013;Silk 2014). However, for an energy-independent diffusion in the TeV nebulae, a dominant contribution of the positron excess by them cannot be ruled out by the current data.…”

Section: Discussionmentioning

confidence: 99%

GeV Observations of the Extended Pulsar Wind Nebulae Constrain the Pulsar Interpretations of the Cosmic-Ray Positron Excess

Liu

Huang

et al. 2019

ApJ

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It has long been suggested that nearby pulsars within ∼1 kpc are the leading candidate of the 10-500 GeV cosmicray positron excess measured by PAMELA and other experiments. The recent measurement of the surface brightness profile of TeV nebulae surrounding Geminga and PSRB0656+14 by the High-Altitude Water Cherenkov Observatory (HAWC) suggests inefficient diffusion of particles from the sources, giving rise to a debate on the pulsar interpretation of the cosmic-ray positron excess. Here we argue that GeV observations provide more direct constraints on the positron density in the TeV nebulae in the energy range of 10-500 GeV and hence on the origin of the observed positron excess. Motivated by this, we search for GeV emission from the TeV nebulae with the Fermi Large Area Telescope (LAT). No spatially extended GeV emission is detected from these two TeV nebulae in the framework of two-zone diffusion spatial templates, suggesting a relatively low density of GeV electrons/positrons in the TeV nebulae. A joint modeling of the data from HAWC and Fermi-LAT disfavors Geminga and PSRB0656+14 as the dominant sources of the positron excess at ∼50-500 GeV for the usual Kolmogorov-type diffusion, while for an energy-independent diffusion, a dominant part of the positron excess contributed by them cannot be ruled out by the current data.

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Section: Discussionmentioning

confidence: 99%

GeV Observations of the Extended Pulsar Wind Nebulae Constrain the Pulsar Interpretations of the Cosmic-Ray Positron Excess

Liu

Huang

et al. 2019

ApJ

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“…Moreover, taking into account standard diffusion and cooling of e ± , the extension of the e ± spectrum up to TeV energies can only be explained if the source is nearby (∼hundreds of parsecs) and middle age (∼hundreds of kyr). Pulsars, as factories of e ± , are one of the proposed candidates to explain the origin of this excess, however there are also more exotic explanations such as galactic jets [1] or dark matter [2]. To measure the maximum energy reached by these e ± at the Earth and unveil the origin of the positron excess is one of the most important questions unsolved in astroparticle physics nowadays.…”

Section: Introductionmentioning

confidence: 99%

Effect of the diffusion parameters on the observed γ -ray spectrum of sources and their contribution to the local all-electron spectrum: The EDGE code

López-Coto

Hahn

BenZvi

et al. 2018

Astroparticle Physics

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The positron excess measured by PAMELA and AMS can only be explained if there is one or several sources injecting them. Moreover, at the highest energies, it requires the presence of nearby (∼hundreds of parsecs) and middle age (maximum of ∼hundreds of kyr) sources. Pulsars, as factories of electrons and positrons, are one of the proposed candidates to explain the origin of this excess. To calculate the contribution of these sources to the electron and positron flux at the Earth, we developed EDGE (Electron Diffusion and Gamma rays to the Earth), a code to treat the propagation of electrons and compute their diffusion from a central source with a flexible injection spectrum. Using this code, we can derive the source's gamma-ray spectrum, spatial extension, the all-electron density in space, the electron and positron flux reaching the Earth and the positron fraction measured at the Earth. We present in this paper the foundations of the code and study how different parameters affect the gamma-ray spectrum of a source and the electron flux measured at the Earth. We also studied the effect of several approximations usually performed in these studies.

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“…Moreover, taking into account standard diffusion and cooling of e ± , the extension of the e ± spectrum up to TeV energies can only be explained if the source is nearby (∼hundreds of parsecs) and middle age (∼hundred of kyr). Pulsars, as factories of e ± , are one of the proposed candidates to explain the origin of this excess, however there are also more exotic explanations such as galactic jets [1] or dark matter [2]. To measure the maximum energy reached by these e ± at the Earth and unveil the origin of the positron excess is one of the most important questions unsolved in astroparticle physics nowadays.…”

Section: Introductionmentioning

confidence: 99%

EDGE: a code to calculate diffusion of cosmic-ray electrons and their gamma-ray emission

López-Coto¹,

Hahn²,

Hinton³

et al. 2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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The positron excess measured by PAMELA and AMS can only be explained if there is one or several sources injecting them. Moreover, at the highest energies, it requires the presence of nearby (∼hundreds of parsecs) and middle age (maximum of ∼hundreds of kyr) source. Pulsars, as factories of electrons and positrons, are one of the proposed candidates to explain the origin of this excess. To calculate the contribution of these sources to the electron and positron flux at the Earth, we developed EDGE (Electron Diffusion and Gamma rays to the Earth), a code to treat diffusion of electrons and compute their diffusion from a central source with a flexible injection spectrum. We can derive the source's gamma-ray spectrum, spatial extension, the all-electron density in space and the electron and positron flux reaching the Earth. We present in this contribution the fundamentals of the code and study how different parameters affect the gamma-ray spectrum of a source and the electron flux measured at the Earth.

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pγ interactions in Galactic jets as a plausible origin of the positron excess

Abstract: The positron flux measured near Earth shows a rise with energy beyond 30 GeV. We show that this rise may be compatible with the production of positrons in pγ interactions in the jets of microquasars.

Cited by 22 publications

References 39 publications

GeV Observations of the Extended Pulsar Wind Nebulae Constrain the Pulsar Interpretations of the Cosmic-Ray Positron Excess

GeV Observations of the Extended Pulsar Wind Nebulae Constrain the Pulsar Interpretations of the Cosmic-Ray Positron Excess

Effect of the diffusion parameters on the observed γ -ray spectrum of sources and their contribution to the local all-electron spectrum: The EDGE code

EDGE: a code to calculate diffusion of cosmic-ray electrons and their gamma-ray emission

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